Joint embedding content neural networks

ABSTRACT

A neural network system can select content based on user and item content embeddings in an approach that can be updated in real time on the user device without server support. Requests for content sent to the server can include an anonymous user embedding that includes data describing the user&#39;s inputs. The content that is nearest to the user embedding in a joint embedding space can be returned as suggested content.

PRIORITY

This application is a continuation of U.S. patent application Ser. No.16/396,119, filed on Apr. 26, 2019, which claims the benefit of priorityto U.S. Provisional Patent Application Ser. No. 62/663,103, filed onApr. 26, 2018, the benefit of priority of each of which is claimedhereby, and each of which is incorporated by reference herein in itsentirety.

TECHNICAL FIELD

The present disclosure generally relates to special-purpose machinesthat manage machine learning processing and improvements to suchvariants, and to the technologies by which such special-purpose machinesbecome improved compared to other special-purpose machines for contentidentification.

BACKGROUND

A user can use a user device (e.g., client device, mobile phone) tobrowse content (e.g., images, video, articles) on websites or throughmobile applications. Some conventional approaches send a user's clickand bookmarked content to network platforms for analysis and torecommend further content to the user. However, some users may preferthat user interaction data be anonymized or stored locally on the clientside. While storing data on the client side may be preferable to someusers, content recommendation may be hampered without transmitting datato network connected recommendation systems for additional content.Further, some client devices lack the processing power andsophistication to perform interaction analysis and recommend contentthat is likely to be of interest or useful to a given user locally onthe device.

BRIEF DESCRIPTION OF THE DRAWINGS

To easily identify the discussion of any particular element or act, themost significant digit or digits in a reference number refer to thefigure (“FIG.”) number in which that element or act is first introduced.

FIG. 1 is a block diagram showing an example messaging system forexchanging data (e.g., messages and associated content) over a network,according to example embodiments.

FIG. 2 is a block diagram illustrating further details regarding themessaging system of FIG. 1 , according to example embodiments.

FIG. 3 is a schematic diagram illustrating data which may be stored in adatabase of a messaging server system, according to certain exampleembodiments.

FIG. 4 is a schematic diagram illustrating a structure of a message,according to some embodiments, generated by a messaging clientapplication for communication.

FIG. 5 is a schematic diagram illustrating an example access-limitingprocess, in terms of which access to content (e.g., an ephemeralmessage, and associated multimedia payload of data) or a contentcollection (e.g., an ephemeral message story) may be time-limited (e.g.,made ephemeral), according to some example embodiments.

FIG. 6 shows an item embedding network, according to some exampleembodiments.

FIG. 7 shows a user embedding network, according to some exampleembodiments.

FIG. 8 shows a joint embedding training architecture, according to someexample embodiments.

FIG. 9 shows example internal functional engines of a joint embeddingsystem, according to some example embodiments.

FIG. 10 shows a flow diagram for a method for recommending content usinga joint embedding, according to some example embodiments.

FIG. 11 shows an example network interaction diagram for anonymouscontent updates, according to some example embodiments.

FIGS. 12A-12D show example user interfaces for a joint embedding system,according to some example embodiments.

FIG. 13 is a block diagram illustrating a representative softwarearchitecture, which may be used in conjunction with various hardwarearchitectures herein described.

FIG. 14 is a block diagram illustrating components of a machine,according to some example embodiments, able to read instructions from amachine-readable medium (e.g., a machine-readable storage medium) andperform any one or more of the methodologies discussed herein.

DETAILED DESCRIPTION

The description that follows includes systems, methods, techniques,instruction sequences, and computing machine program products thatembody illustrative embodiments of the disclosure. In the followingdescription, for the purposes of explanation, numerous specific detailsare set forth in order to provide an understanding of variousembodiments of the inventive subject matter. It will be evident,however, to those skilled in the art, that embodiments of the inventivesubject matter may be practiced without these specific details. Ingeneral, well-known instruction instances, protocols, structures, andtechniques are not necessarily shown in detail.

As discussed, content recommendation can be difficult to perform on theclient device side. To this end, a joint content system can beimplemented to efficiently analyze user interactions and recommendcontent on the user's device, without needing to connect to a serverplatform for user embedding support; and, according to some embodiments,without needing to connect to the server platform to identify the mostrelevant or useful content for a given user. The following discussion isseparated into three parts based on the three components of the jointcontent system.

(1) Real-time on-device embedding updates in constant time: In someconventional approaches, updating user data in a machine-learning-basedrecommender system requires retraining of the machine learning model orrequires a complete reconstruction of the user representation from allavailable data about the user. The first of these is prohibitive forapplications where the user data (and the associated recommendations)are to be updated in real-time as the user selects objects (e.g., clickson items). The second is problematic because it causes the performanceof user updates to decrease over time as more data about the user isaccumulated, and further because reconstruction can additionally requirethat user history be continuously stored so long as the system is tooperate, which may not be ideal for storage cost or privacy preferences.The joint embedding system avoids these issues by enabling a userembedding and interaction history on the user's mobile device withoutserver support based on recursive state data as further discussed below.

(2) Bipartite triplet embeddings to preserve relative distances:Conventional triplet-embedding based recommender schemes are trained topreserve ordinal relationships, but do not have a mechanism forpreserving distances between different classes of information (e.g.,user data and content item data). The lack of distance preservation canbe an issue for creating a joint user-item (e.g., data item) embeddingmechanism that captures relationships between users and items that aredefined in terms of numerical scalar values (as opposed to simpleordinal or binary relationships). To this end, the joint content systemis configured to derive real-valued engagement scores that capture thedegree to which a user engages with a particular data item (e.g.,article, social network site story, image, video, another user'sprofile, etc.). The real-valued engagement scores of the joint contentsystem are an improvement over conventional approaches that do notinclude a mechanism for embedding these values without treating thevalues as binary scores and throwing away much of the usefulinformation.

(3) Privacy-preserving user representations for embedding-basedrecommender systems: Conventional recommender approaches require thestorage of user-specific representations attached to an identifier forthat user. For machine learning algorithms that require server-sidetraining, a user identifier has to be passed to the server alongside theuser's data. Though some approaches attempt to anonymize the identifier,anonymization in those approaches needs to be done in a reversiblemanner that permits the recovery of the original user identifier toallow the trained model to perform recommendations for the given user.Some conventional approaches may handle the requirement of reversibilityby storing some of a given user's information on the server-side in amanner that can potentially be identified. This may not be desired byusers from based on their data privacy preferences, because if theserver is breached (e.g., hacked) the user's data may be exposed tomalicious entities. The joint embedding system can avoid these issues byusing the joint embedding space that enables a user embedding to beupdated on the user's client device side, and request content from theserver in a secure fashion via the user embedding, as the user embeddingis a complex and dynamic feature space representation in n dimensions ofthe joint embedding space that obfuscates the user's identity.

FIG. 1 shows a block diagram of an example messaging system 100 forexchanging data (e.g., messages and associated content) over a network106. The messaging system 100 includes multiple client devices 102, eachof which hosts a number of applications including a messaging clientapplication 104. Each messaging client application 104 iscommunicatively coupled to other instances of the messaging clientapplication 104 and a messaging server system 108 via the network 106(e.g., the Internet).

Accordingly, each messaging client application 104 is able tocommunicate and exchange data with another messaging client application104 and with the messaging server system 108 via the network 106. Thedata exchanged between messaging client applications 104, and between amessaging client application 104 and the messaging server system 108,includes functions (e.g., commands to invoke functions) as well aspayload data (e.g., text, audio, video, or other multimedia data).

The messaging server system 108 provides server-side functionality viathe network 106 to a particular messaging client application 104. Whilecertain functions of the messaging system 100 are described herein asbeing performed by either a messaging client application 104 or by themessaging server system 108, it will be appreciated that the location ofcertain functionality within either the messaging client application 104or the messaging server system 108 is a design choice. For example, itmay be technically preferable to initially deploy certain technology andfunctionality within the messaging server system 108, and to latermigrate this technology and functionality to the messaging clientapplication 104 where a client device 102 has a sufficient processingcapacity.

The messaging server system 108 supports various services and operationsthat are provided to the messaging client application 104. Suchoperations include transmitting data to, receiving data from, andprocessing data generated by the messaging client application 104. Thisdata may include message content, client device information, geolocationinformation, media annotation and overlays, message content persistenceconditions, social network information, and live event information, asexamples. Data exchanges within the messaging system 100 are invoked andcontrolled through functions available via user interfaces (UIs) of themessaging client application 104.

Turning now specifically to the messaging server system 108, anapplication programming interface (API) server 110 is coupled to, andprovides a programmatic interface to, an application server 112. Theapplication server 112 is communicatively coupled to a database server118, which facilitates access to a database 120 in which is stored dataassociated with messages processed by the application server 112.

The API server 110 receives and transmits message data (e.g., commandsand message payloads) between the client devices 102 and the applicationserver 112. Specifically, the API server 110 provides a set ofinterfaces (e.g., routines and protocols) that can be called or queriedby the messaging client application 104 in order to invoke functionalityof the application server 112. The API server 110 exposes variousfunctions supported by the application server 112, including accountregistration; login functionality; the sending of messages, via theapplication server 112, from a particular messaging client application104 to another messaging client application 104; the sending of mediafiles (e.g., images or video) from a messaging client application 104 toa messaging server application 114 for possible access by anothermessaging client application 104; the setting of a collection of mediadata (e.g., a story); the retrieval of such collections; the retrievalof a list of friends of a user of a client device 102; the retrieval ofmessages and content; the adding and deletion of friends to and from asocial graph; the location of friends within the social graph; andopening application events (e.g., relating to the messaging clientapplication 104).

The application server 112 hosts a number of applications andsubsystems, including the messaging server application 114, an imageprocessing system 116, a social network system 122, and a server-sidejoint embedding system 150. The messaging server application 114implements a number of message-processing technologies and functions,particularly related to the aggregation and other processing of content(e.g., textual and multimedia content) included in messages receivedfrom multiple instances of the messaging client application 104. As willbe described in further detail, the text and media content from multiplesources may be aggregated into collections of content (e.g., calledstories or galleries). These collections are then made available, by themessaging server application 114, to the messaging client application104. Other processor- and memory-intensive processing of data may alsobe performed server-side by the messaging server application 114, inview of the hardware requirements for such processing.

The application server 112 also includes the image processing system116, which is dedicated to performing various image processingoperations, typically with respect to images or video received withinthe payload of a message at the messaging server application 114.

The social network system 122 supports various social networkingfunctions and services, and makes these functions and services availableto the messaging server application 114. To this end, the social networksystem 122 maintains and accesses an entity graph (e.g., entity graph304 in FIG. 3 ) within the database 120. Examples of functions andservices supported by the social network system 122 include theidentification of other users of the messaging system 100 with whom aparticular user has relationships or whom the particular user is“following,” and also the identification of other entities and interestsof a particular user. The application server 112 is communicativelycoupled to a database server 118, which facilitates access to a database120 in which is stored data associated with messages processed by themessaging server application 114.

The joint embedding system 150 is an instance of the joint embeddingexecuted on the server-side from application server 112. In some exampleembodiments, the server-side joint embedding system 150 performs taskssuch as joint model training, nearest neighbor analysis, and contentresponses (e.g., in response to content requests from the message clientapplication 104).

FIG. 2 is a block diagram illustrating further details regarding themessaging system 100, according to example embodiments. Specifically,the messaging system 100 is shown to comprise the messaging clientapplication 104 and the application server 112, which in turn embody anumber of subsystems, namely an ephemeral timer system 202, a collectionmanagement system 204, an annotation system 206, and a client-side jointembedding system 210.

The ephemeral timer system 202 is responsible for enforcing thetemporary access to content permitted by the messaging clientapplication 104 and the messaging server application 114. To this end,the ephemeral timer system 202 incorporates a number of timers that,based on duration and display parameters associated with a message orcollection of messages (e.g., a story), selectively display and enableaccess to messages and associated content via the messaging clientapplication 104. Further details regarding the operation of theephemeral timer system 202 are provided below.

The collection management system 204 is responsible for managingcollections of media (e.g., collections of text, image, video, and audiodata). In some examples, a collection of content (e.g., messages,including images, video, text, and audio) may be organized into an“event gallery” or an “event story.” Such a collection may be madeavailable for a specified time period, such as the duration of an eventto which the content relates. For example, content relating to a musicconcert may be made available as a “story” for the duration of thatmusic concert. The collection management system 204 may also beresponsible for publishing an icon that provides notification of theexistence of a particular collection to the user interface of themessaging client application 104.

The collection management system 204 furthermore includes a curationinterface 208 that allows a collection manager to manage and curate aparticular collection of content. For example, the curation interface208 enables an event organizer to curate a collection of contentrelating to a specific event (e.g., delete inappropriate content orredundant messages). Additionally, the collection management system 204employs machine vision (or image recognition technology) and contentrules to automatically curate a content collection. In certainembodiments, compensation may be paid to a user for inclusion ofuser-generated content into a collection. In such cases, the curationinterface 208 operates to automatically make payments to such users forthe use of their content.

The annotation system 206 provides various functions that enable a userto annotate or otherwise modify or edit media content associated with amessage. For example, the annotation system 206 provides functionsrelated to the generation and publishing of media overlays for messagesprocessed by the messaging system 100. The annotation system 206operatively supplies a media overlay (e.g., a geofilter or filter) tothe messaging client application 104 based on a geolocation of theclient device 102. In another example, the annotation system 206operatively supplies a media overlay to the messaging client application104 based on other information, such as social network information ofthe user of the client device 102. A media overlay may include audio andvisual content and visual effects. Examples of audio and visual contentinclude pictures, text, logos, animations, and sound effects. An exampleof a visual effect includes color overlaying. The audio and visualcontent or the visual effects can be applied to a media content item(e.g., a photo) at the client device 102. For example, the media overlayincludes text that can be overlaid on top of a photograph generated bythe client device 102. In another example, the media overlay includes anidentification of a location (e.g., Venice Beach), a name of a liveevent, or a name of a merchant (e.g., Beach Coffee House). In anotherexample, the annotation system 206 uses the geolocation of the clientdevice 102 to identify a media overlay that includes the name of amerchant at the geolocation of the client device 102. The media overlaymay include other indicia associated with the merchant. The mediaoverlays may be stored in the database 120 and accessed through thedatabase server 118.

In one example embodiment, the annotation system 206 provides auser-based publication platform that enables users to select ageolocation on a map and upload content associated with the selectedgeolocation. The user may also specify circumstances under whichparticular content should be offered to other users. The annotationsystem 206 generates a media overlay that includes the uploaded contentand associates the uploaded content with the selected geolocation.

In another example embodiment, the annotation system 206 provides amerchant-based publication platform that enables merchants to select aparticular media overlay associated with a geolocation via a biddingprocess. For example, the annotation system 206 associates the mediaoverlay of a highest-bidding merchant with a corresponding geolocationfor a predefined amount of time.

As discussed in further detail below, client-side joint embedding systemis configured generate and update a user embedding, and identify content(e.g., locally or via server) using the user embeddings, as discussed infurther detail below.

FIG. 3 is a schematic diagram illustrating data 300 which may be storedin the database 120 of the messaging server system 108, according tocertain example embodiments. While the content of the database 120 isshown to comprise a number of tables, it will be appreciated that thedata 300 could be stored in other types of data structures (e.g., as anobject-oriented database).

The database 120 includes message data stored within a message table314. An entity table 302 stores entity data, including an entity graph304. Entities for which records are maintained within the entity table302 may include individuals, corporate entities, organizations, objects,places, events, and so forth. Regardless of type, any entity regardingwhich the messaging server system 108 stores data may be a recognizedentity. Each entity is provided with a unique identifier, as well as anentity type identifier (not shown).

The entity graph 304 furthermore stores information regardingrelationships and associations between or among entities. Suchrelationships may be social, professional (e.g., work at a commoncorporation or organization), interest-based, or activity-based, forexample.

The database 120 also stores annotation data, in the example form offilters, in an annotation table 312. Filters for which data is storedwithin the annotation table 312 are associated with and applied tovideos (for which data is stored in a video table 310) and/or images(for which data is stored in an image table 308). Filters, in oneexample, are overlays that are displayed as overlaid on an image orvideo during presentation to a recipient user. Filters may be of varioustypes, including user-selected filters from a gallery of filterspresented to a sending user by the messaging client application 104 whenthe sending user is composing a message. Other types of filters includegeolocation filters (also known as geo-filters), which may be presentedto a sending user based on geographic location. For example, geolocationfilters specific to a neighborhood or special location may be presentedwithin a user interface by the messaging client application 104, basedon geolocation information determined by a Global Positioning System(GPS) unit of the client device 102. Another type of filter is a datafilter, which may be selectively presented to a sending user by themessaging client application 104, based on other inputs or informationgathered by the client device 102 during the message creation process.Examples of data filters include a current temperature at a specificlocation, a current speed at which a sending user is traveling, abattery life for a client device 102, or the current time.

Other annotation data that may be stored within the image table 308 isso-called “lens” data. A “lens” may be a real-time special effect andsound that may be added to an image or a video.

As mentioned above, the video table 310 stores video data which, in oneembodiment, is associated with messages for which records are maintainedwithin the message table 314. Similarly, the image table 308 storesimage data associated with messages for which message data is stored inthe message table 314. The entity table 302 may associate variousannotations from the annotation table 312 with various images and videosstored in the image table 308 and the video table 310.

A story table 306 stores data regarding collections of messages andassociated image, video, or audio data, which are compiled into acollection (e.g., a story or a gallery). The creation of a particularcollection may be initiated by a particular user (e.g., each user forwhom a record is maintained in the entity table 302). A user may createa “personal story” in the form of a collection of content that has beencreated and sent/broadcast by that user. To this end, the user interfaceof the messaging client application 104 may include an icon that isuser-selectable to enable a sending user to add specific content to hisor her personal story.

A collection may also constitute a “live story,” which is a collectionof content from multiple users that is created manually, automatically,or using a combination of manual and automatic techniques. For example,a “live story” may constitute a curated stream of user-submitted contentfrom various locations and events. Users whose client devices 102 havelocation services enabled and are at a common location or event at aparticular time may, for example, be presented with an option, via auser interface of the messaging client application 104, to contributecontent to a particular live story. The live story may be identified tothe user by the messaging client application 104 based on his or herlocation. The end result is a “live story” told from a communityperspective.

A further type of content collection is known as a “location story,”which enables a user whose client device 102 is located within aspecific geographic location (e.g., on a college or university campus)to contribute to a particular collection. In some embodiments, acontribution to a location story may require a second degree ofauthentication to verify that the end user belongs to a specificorganization or other entity (e.g., is a student on the universitycampus).

FIG. 4 is a schematic diagram illustrating a structure of a message 400,according to some embodiments, generated by a messaging clientapplication 104 for communication to a further messaging clientapplication 104 or the messaging server application 114. The content ofa particular message 400 is used to populate the message table 314stored within the database 120, accessible by the messaging serverapplication 114. Similarly, the content of a message 400 is stored inmemory as “in-transit” or “in-flight” data of the client device 102 orthe application server 112. The message 400 is shown to include thefollowing components:

-   -   A message identifier 402: a unique identifier that identifies        the message 400.    -   A message text payload 404: text, to be generated by a user via        a user interface of the client device 102 and that is included        in the message 400.    -   A message image payload 406: image data captured by a camera        component of a client device 102 or retrieved from memory of a        client device 102, and that is included in the message 400.    -   A message video payload 408: video data captured by a camera        component or retrieved from a memory component of the client        device 102, and that is included in the message 400.    -   A message audio payload 410: audio data captured by a microphone        or retrieved from the memory component of the client device 102,        and that is included in the message 400.    -   Message annotations 412: annotation data (e.g., filters,        stickers, or other enhancements) that represents annotations to        be applied to the message image payload 406, message video        payload 408, or message audio payload 410 of the message 400.    -   A message duration parameter 414: a parameter value indicating,        in seconds, the amount of time for which content of the message        400 (e.g., the message image payload 406, message video payload        408, and message audio payload 410) is to be presented or made        accessible to a user via the messaging client application 104.    -   A message geolocation parameter 416: geolocation data (e.g.,        latitudinal and longitudinal coordinates) associated with the        content payload of the message 400. Multiple message geolocation        parameter 416 values may be included in the payload, with each        of these parameter values being associated with respective        content items included in the content (e.g., a specific image in        the message image payload 406, or a specific video in the        message video payload 408).    -   A message story identifier 418: values identifying one or more        content collections (e.g., “stories”) with which a particular        content item in the message image payload 406 of the message 400        is associated. For example, multiple images within the message        image payload 406 may each be associated with multiple content        collections using identifier values.    -   A message tag 420: one or more tags, each of which is indicative        of the subject matter of content included in the message        payload. For example, where a particular image included in the        message image payload 406 depicts an animal (e.g., a lion), a        tag value may be included within the message tag 420 that is        indicative of the relevant animal. Tag values may be generated        manually, based on user input, or may be automatically generated        using, for example, image recognition.    -   A message sender identifier 422: an identifier (e.g., a        messaging system identifier, email address, or device        identifier) indicative of a user of the client device 102 on        which the message 400 was generated and from which the message        400 was sent.    -   A message receiver identifier 424: an identifier (e.g., a        messaging system identifier, email address, or device        identifier) indicative of a user of the client device 102 to        which the message 400 is addressed.

The contents (e.g., values) of the various components of the message 400may be pointers to locations in tables within which content data valuesare stored. For example, an image value in the message image payload 406may be a pointer to (or address of) a location within the image table308. Similarly, values within the message video payload 408 may point todata stored within the video table 310, values stored within the messageannotations 412 may point to data stored in the annotation table 312,values stored within the message story identifier 418 may point to datastored in the story table 306, and values stored within the messagesender identifier 422 and the message receiver identifier 424 may pointto user records stored within the entity table 302.

FIG. 5 is a schematic diagram illustrating an access-limiting process500, in terms of which access to content (e.g., an ephemeral message502, and associated multimedia payload of data) or a content collection(e.g., an ephemeral message story 504) may be time-limited (e.g., madeephemeral), according to some example embodiments. 100541 An ephemeralmessage 502 is shown to be associated with a message duration parameter506, the value of which determines an amount of time that the ephemeralmessage 502 will be displayed to a receiving user of the ephemeralmessage 502 by the messaging client application 104. In one embodiment,where the messaging client application 104 is an application client, anephemeral message 502 is viewable by a receiving user for up to amaximum of 10 seconds, depending on the amount of time that the sendinguser specifies using the message duration parameter 506.

The message duration parameter 506 and the message receiver identifier424 are shown to be inputs to a message timer 512, which is responsiblefor determining the amount of time that the ephemeral message 502 isshown to a particular receiving user identified by the message receiveridentifier 424. In particular, the ephemeral message 502 will only beshown to the relevant receiving user for a time period determined by thevalue of the message duration parameter 506. The message timer 512 isshown to provide output to a more generalized ephemeral timer system202, which is responsible for the overall timing of display of content(e.g., an ephemeral message 502) to a receiving user.

The ephemeral message 502 is shown in FIG. 5 to be included within anephemeral message story 504 (e.g., a personal story, or an event story).The ephemeral message story 504 has an associated story durationparameter 508, a value of which determines a time duration for which theephemeral message story 504 is presented and accessible to users of themessaging system 100. The story duration parameter 508, for example, maybe the duration of a music concert, where the ephemeral message story504 is a collection of content pertaining to that concert.Alternatively, a user (either the owning user or a curator user) mayspecify the value for the story duration parameter 508 when performingthe setup and creation of the ephemeral message story 504.

Additionally, each ephemeral message 502 within the ephemeral messagestory 504 has an associated story participation parameter 510, a valueof which determines the duration of time for which the ephemeral message502 will be accessible within the context of the ephemeral message story504. Accordingly, a particular ephemeral message 502 may “expire” andbecome inaccessible within the context of the ephemeral message story504, prior to the ephemeral message story 504 itself expiring in termsof the story duration parameter 508.

The ephemeral timer system 202 may furthermore operationally remove aparticular ephemeral message 502 from the ephemeral message story 504based on a determination that it has exceeded an associated storyparticipation parameter 510. For example, when a sending user hasestablished a story participation parameter 510 of 24 hours fromposting, the ephemeral timer system 202 will remove the relevantephemeral message 502 from the ephemeral message story 504 after thespecified 24 hours. The ephemeral timer system 202 also operates toremove an ephemeral message story 504 either when the storyparticipation parameter 510 for each and every ephemeral message 502within the ephemeral message story 504 has expired, or when theephemeral message story 504 itself has expired in terms of the storyduration parameter 508.

In response to the ephemeral timer system 202 determining that anephemeral message story 504 has expired (e.g., is no longer accessible),the ephemeral timer system 202 communicates with the messaging system100 (e.g., specifically, the messaging client application 104) to causean indicium (e.g., an icon) associated with the relevant ephemeralmessage story 504 to no longer be displayed within a user interface ofthe messaging client application 104.

A detailed description of the joint embedding system is included here,followed by an example using user data and story data with reference toFIGS. 6-8 , followed by example joint embedding methods in FIGS. 9 and10 , and example user interfaces in FIGS. 12A-12D.

The joint embedding system is designed to embed users and items in thesame space (e.g., embedding space, feature space) in a manner thatrespects relative distance relations defined between users and items(e.g., content items, images, articles, videos, friend posts, etc.).This allows recommendations to be generated by finding the nearest itemneighbors to a given user (e.g., nearest neighbor to that user'sembedding in the shared embedding space). According to some exampleembodiments, the embeddings are generated by two separate networks: anitem embedding network for embedding items of content, and a userembedding network for embedding users.

The item embedding network is a learned mapping between an item propertyvector (e.g., a vector from item properties or attributes, such astitle, view count, length) and an embedding vector generated from theitem (e.g., an embedding vector generated by a fully connected neuralnetwork). The user embedding network is a learned mapping between a userattribute vector (e.g., a vector from user properties, such as gender,age, location, user interests) and a sequence of user-item interactionvectors from user interactions with content generated by a neuralnetwork (e.g., a recurrent neural network). The user embedding networkis configured in a manner that enables efficient updating of the userembedding and the subsequent recommendations without contacting theserver. The user embedding network is also constructed so as to enablethe preservation of user privacy because the complex dynamic userembedding obfuscates the user's identity. According to some exampleembodiments, training is performed using triplet loss and a dual neuralnetwork (e.g., a Siamese neural network) that preserves relativenumerical distances between the user embeddings and item embeddings.

The user embedding network is configured to update user representationsin real-time without storing the user's full interaction history. Thisis enabled via utilizing a neural network to create a content-basedrepresentation of each user where there is no distinct representationlearned for each particular user. This approach is in contrast toconventional collaborative-filtering based approaches that learnrepresentations for each user based on sophisticated global inference ofrepresentations.

In the user embedding network, the user is represented using acombination of the user's attributes (such as their gender, their agegroup, their country code, etc.) and the user's history of interactionwith the system (e.g., content provided by messaging client application104). The user's interaction history is captured as the items the userclicked on, the properties of these items (headline, publisherdescription, etc.) and the properties of the user-item interactions (howlong they viewed the item, what time they viewed the item, where theitem appeared in the user's item feed in messaging client application104, etc.) The fact that the user is represented in terms of contentinstead of an identifier means that the joint model can learn togenerate a user embedding based on the known properties of a userinstead of relying on learning a unique representation for each user.This allows new users to be added to the joint embedding system withoutretraining the model, and further allows users' embeddings to be updatedby updating the content used to generate respective userrepresentations.

The user embedding is also generated using a more semi-staticrepresentation of the user: a user vector generated using user attributeor profile data (e.g., age, gender, likes, country, etc.). Since auser's attributes are represented by the fixed length vector, updatingthese attributes takes only constant time.

In contrast, the user interaction history has an indefinite length, andcannot prima facie be updated without memorizing this history andrecomputing the user representation by going through the history. Thistakes linear time in the length of the history and therefore gets sloweras more history is acquired. However, to this end, the recurrent neuralnetwork manages the indefinite length history as follows.

In some example embodiments, the user embedding network implements arecurrent neural network (e.g., a long short-term memory (LSTM) network)to represent the user interaction history, which conventionally requiresthe re-computation of the user interaction history to update. In someexample embodiments, the user embedding network only stores the finalhidden state (e.g., recurrent state data of a previous sum ofinteractions) of the recurrent neural network on the user's device. Inthis way, updating the user embedding only requires a state update tothe hidden state and additional and the new interaction information.Since the size of this state representation is independent of the lengthof the user interaction history, this representational scheme allows theuser embedding network to update the user embedding representation onthe device using an amount of computation independent of the userinteraction history and does not require that the joint embedding systemstore the user interaction history on the device, according to someexample embodiments.

As mentioned, the user data and the content data can be embedded in ajoint embedding space that allows for relevant or useful content to befound by determining the nearest item embeddings to the current userembedding in the shared space. In some example embodiments, a jointembedding architecture is implemented using bipartite triplet embeddingsto preserve relative distances between the different classes ofinformation (users, content). In some example embodiments, the jointembedding architecture implements an objective function that smoothlycaptures the desired properties out of which the desired embedding willemerge when trained on a dataset using a triplet loss and gradientdescent optimization.

The embeddings are obtained by training a neural network to generateuser and item embeddings (to learn a function from raw user propertiesto a user vector and a function from raw item properties to an itemvector) that satisfy this objective function. This function is derivedas follows using the following notation:

-   U: An example user that to be embedded.-   I₁: An example item to be embedded (for which there is a distance    defined between I₁ and U)-   I₂: Another example item to be embedded (for which there is a    distance defined between I₂ and U)-   D₁: Ground truth distance from I₁ to U-   D₂: Ground truth distance from I₂ to U-   E_(I1): I1 embedding-   E_(I2): I₂ embedding-   E_(U): User embedding-   S(E₁,E₂): Distance function between two embeddings (for example, the    Euclidean distance)

The objective function is as followed, according to some exampleembodiments:

argmin(log(sigmoid((D ₁ −D ₂)*S(E _(I1) ,E _(U))−(D ₁ −D ₂)*S(E _(I2) ,E_(U)))))

The above objective function is based on a reification of the modelingobjective that users should be closer to items that they are more likelyto enjoy:

IF D₁ > D₂:  THEN minimize (S(E_(I2), E_(U)) − S(E_(I1), E_(U))) ELIF D₁< D₂:  THEN minimize (S(E_(I1), E_(U)) − S(E_(I2), E_(U))) ELSE (D₁ =D₂):  THEN don't do anything

The above encapsulates the following: the distance between a user and anitem that the user enjoys more should be smaller than this distancebetween that user and an item that they enjoy less. Further, by noticingthe continuity of the relationship, additional smoothness properties canbe included; in particular:

D ₁ −D ₂ ∝S(E _(I1) ,E _(U))−S(E _(I2) ,E _(U))

error=(S(E _(I1) ,E _(U))−S(E _(I2) ,E _(U)))−c(D ₁ −D ₂) (where c is aconstant)

This formulation captures the notion that the degree to which the modelis wrong (e.g., the error) is proportional both to the differences ofpredicted distances between the two items and the user and thedifference between the ideal distances between the two items and theuser. Increasing the ideal distance (e.g., a higher true gap betweenuser-item preferences) increases the error and increasing the predicteddistance also increases the error.

However, the above does not take the form of a triplet objective, whichneeds to be expressed in terms of a specific quantity to be minimizedlocally (the constant makes this difficult, since it is a globalparameter that is not known). To this end, this expression:argmin((D₁−D₂)(S(E_(I1), E_(U))−S(E_(I2), E_(U))), is modified to arriveat: argmin((D₁−D₂)*S(E_(I1), E_(U))−(D₁−D₂)*S(E_(I2), E_(U))), thelatter of which allows computations of contributions of both itemdistances separately.

A ranking triplet loss is introduced by way of including a sigmoidfunction and a logarithm function, which yields an objective function:argmin(log(sigmoid((D₁−D₂)*S(E_(I1), E_(U))−(D₁−D₂)*S(E_(I2), E_(U))))).This function has desirable properties, as the output of thelog(sigmoid((D₁−D₂)*S(E_(I1), E_(U))−(D₁−D₂)*S(E_(I2), E_(U)))))component is proportional to the ordinal probability that a user prefersitem 1 to item 2, weighted by the degree to which the user prefers item1 to item 2. If it is additionally assumed that the observed preferencedegrees are sampled from a normal distribution centered around the truepreference degrees, then the above reduces to the numerical probabilitythat a user prefers item 1 to item 2, weighted by the degree to whichthe user prefers item 1 to item 2, as informed by additional informationabout the degree of the preference. If the function is optimized using agradient method (e.g., stochastic gradient descent), then the resultantgradients are proportional in magnitude to the differences in user-itempreferences, inducing greater pressure for the algorithm to produce therelative ranking correct between items with a large difference inpreference for a given user than for those with a smaller difference inpreference. The gradient pressure on various items for a given user isequivalent when the distances between the items and that user areproportional to the ground truth similarities (e.g., the user-itemengagement scores). When this is applied to an entire dataset, theresult is for items to lie near users for which they are likely to havehigh engagement and far from users that are likely to have lowengagement. Furthermore, users with similar preferences lie near eachother and items that elicit similar user behaviors should lie near eachother.

As mentioned, the user embedding network further preserves user dataprivacy. In particular, because the embedding network represents usersby their interaction history (e.g., in a user embedding) instead of by aunique identifier or a unique stored representation, identification ofthe user is impractical. The anonymity aspect of the user embedding isenabled via the system providing recommendations based on raw userattributes and interaction history, and does not require the learning ofindividual user-specific representations that would need to bemaintained on the server and transmitted back to their respective users(which would require maintaining a reversible identifier for that userattached to the user's attribute and interaction information on theserver).

In some example embodiments, to prevent server-side identification ofuser data, the data is separated into three components based on wherethe data is stored and transmitted. The components are the user'sdevice, the server, and the transmissions (e.g., content requests).

In some example embodiments, the server contains information aboutinteraction history of platform users, but without any reversible useridentifiers attached. Using this representation, the server cannotidentify specific users, as it contains no information linking any ofthe statistical data to users' themselves (not even encryptedinformation). In some example embodiments, the device stores a user'sinteraction history as well as the user's personal information, but doesnot contain any information about other users. In some exampleembodiments, the transmissions may contain user attribute andinteraction history information without any reversible identifierinformation, or may separately contain user embeddings or item content.In this way, user's client devices send attribute and interaction datato the server in a completely anonymized manner (e.g., via embedding)without including any information that would allow the server toidentify the user to which the data belonged. This anonymous datatransmission is akin to locking the door and throwing away the key thatwould enable the server to map the data back to a specific user.

In some example embodiments, the joint embedding architecture of thesystem is trained server-side by learning to directly embed userinteraction histories and item properties into a shared space thatpreserves relative co-locality of users and items with high affinity.The result of the training is a pair of functions: one for mapping a setof item properties to an item embedding and another for mapping a set ofuser properties and interaction history to a user embedding. Thesefunctions (e.g., the trained user embedding network, the traineditem/content embedding network) are transmitted from the server to thedevice, and further can be maintained on both the server and the device,according to some example embodiments. In some example embodiments, thecontent embedding network is only transferred to the user client devicein those implementations where the user device is to perform generationof an item embedding for real-time, on-device ranking and re-ranking ofcontent items.

Given these learned functions recommendations for content can begenerated by embedding a user's interaction history on the device(either using a saved representation of the full interaction history orusing a condensed representation) and sending this embedding to theserver as a query to retrieve recommended items based on an approximatenearest-neighbor retrieval scheme. Though this embedding may be sent tothe server in a reversibly identifiable manner (e.g., as a request froman identifiable client device), the user data does not in itself containinterpretable information about the user as it is a dynamic embedding(e.g., changing per interactions, per content, per userattribute/profile vector changes) and therefore user privacy ispreserved.

In some example embodiments, content recommendations can also beobtained by embedding items and the user on device and computing thenearest neighbor function (e.g., Euclidean distance, inner product, knearest neighbors) without communicating with the server, Further, sincethe server contains no information that would allow the association ofuser attribute and interaction information with a particular user—evenif decrypted—network sites that implement joint embedding system (e.g.,messaging server system 108 and application server 112) can maintain ahigher level of user privacy than conventional approaches.

FIG. 6 shows an item embedding network 600, according to some exampleembodiments. In the example illustrated, the item embedding network is afully connected neural network that receives content data (e.g., storydata) as input data 605, and generates (via hidden layers, “H_(1,2),H_(1,2), H_(1,3) . . . ”) the output data 610, which in the illustratedexample is the story embedding that can be used for nearest neighbordeterminations. As discussed here, a story is a multi-part electronicdocument having multiple pages, where each page can correspond to a fullscreen image, video or article portion. Although story and storyembeddings are discussed here as an example, it is appreciated that thecontent items can be other items such as audio files, website webpages,user posts of a HTML website, streaming content files identified bynetwork addresses (e.g., URL), and so on.

Example features (e.g., “Feat₁ . . . ”) of a content item can include,for example, story edition headline data (a topic mixture vector), apublisher description data (a topic mixture vector), number of ephemeralmessages in the edition (numeric), edition tap or interaction count(numeric), edition impression count or display count (numeric) for astory, and so on. The output data 610 is an item embedding with ndimensions. After the joint embedding model is trained (discussed belowwith reference to FIG. 8 ), the item embedding network 600 can readilygenerate new content embeddings by inputting new input data into theitem embedding network 600 and storing the output data (e.g., the newcontent item embedding).

FIG. 7 shows a user embedding network 700, according to some exampleembodiments. The user embedding network 700 is a learned mapping betweena user attribute vector and a sequence of user-item interaction vectors.The user embedding network 700 is configured to enable efficientupdating of the user representation and the subsequent recommendationswithout contacting the server. The elements use the following notations:

S_(i)—Story representation interacted with at step i

I_(i)—Interaction type at observation i

H_(i)—RNN hidden state at observation i

U_(S)—User LSTM hidden state output

U_(I)—Total user interaction representation for user u

U_(A)—User attribute representation (vector)

UE—User embedding (used to find nearest neighbors)

Examples of user attribute embeddings (“U_(A)”) include: country code(one-hot); region (one-hot); gender (one-hot); age group (one-hot);friend count (numeric); account age (numeric); user interests (vector ofdifferent interest category scores)

Examples of user interaction embeddings (“U_(I)”) include: allindividual item features; date (numeric); position shown in story/itemfeed (one-hot); whether user clicked (one-hot); story/post view ratio(numeric); channel engagement score (numeric); whether partial view(one-hot); seconds since last tap (numeric); featured tap count(numeric); channel tap count (numeric); channel unique tap count(numeric); cell view count (numeric); unique cell view count (numeric);edition age (numeric); minute of day (numeric); day of week (one-hot);is subscribed (one-hot), and so on.

As illustrated, according to some example embodiments, the userembedding network comprises a recurrent neural network 710 (RNN) thatgenerates a hidden user interaction state (U_(S)) for later updates tothe user embedding, and the current user interaction embedding forn-interactions of user history. The user embedding network 700 furthercomprises a fully connected (feed forward (FF)) neural network thatgenerates the user embedding, U_(E), from the user interaction embeddingU_(I) and the user attribute or profile vector U_(A).

Further, although content and users are discussed here for the jointembedding space as an example, it is appreciated that the jointembeddings space can be configured for two different classes of dataother than users and user interface content items. For example, audiodata could be embedded via the item embedding network 600 by usingfeatures that describe the given audio file as input data. Further, userinteraction data could be play count, duration of play, and so on. It isfurther appreciated that the user embeddings need not data of users, butrather data that is continuously updated. For example, instead of userembeddings, an automobile embedding can be continually updated via therecurrent neural network to capture the current state of a givenautomobiles performance, and the item embeddings, continuing theexample, are new parts that are installed in the automobile, where someparts perform better with a given vehicle than others. For example,platinum spark plugs would correspond to a story item embedding, andperformance in different cars (which correspond to users) can be trackedby putting the car embeddings in the parts embedding space, such thatparts can be recommended via nearest neighbor distance metrics asdiscussed above.

FIG. 8 shows a joint embedding training architecture 800, according tosome example embodiments. The joint content training architecture 800 isconfigured to embed users and items in the same space in a manner thatrespects relative distance relations defined between users and items,according to some example embodiments. This approach enables new contentto be selected and recommended to a user by determining the nearest itemneighbors to a given user embedding. The elements are denoted asfollows:

I_(u,s)—Interaction score between user u∈U and story s∈S

U_(I)—User interaction representation (RNN output)

U_(A)—User attribute representation

S_(R)—Positive story raw representation embedding (e.g., generated byitem embedding network 600)

S_(A)—Positive story attributes (e.g., attribute vector fromfeatures/attributes of positive story)

N_(R)—Negative story raw representation embedding (e.g., generated byitem embedding network 600)

N_(A)—Negative story attributes (e.g., attribute vector fromfeatures/attributes of negative story)

U_(E)—User embedding

S_(E)—Story embedding N_(E)—Negative story embedding

In the example joint training architecture 800, two item embeddingnetworks are implemented for training: a positive story embeddingnetwork 805, and a negative story embedding network 810. The positiveand negative story embedding networks are used in training to train theuser embedding network 800 (e.g., the weights in network 807) so thatthe user embedding is in the space shared space as the story space asdiscussed above. Further, the recursive neural network portion notdepicted in FIG. 8 to clarify the overall layout of the trainingarchitecture. Further, as illustrated in FIG. 8 , the story embeddingnetworks may be differently configured during training and at runtime.For example, positive story embedding network 805 and negative storyembedding network 810 receive story attributes and raw embeddings asinputs, whereas the runtime item embeddings network 600 in FIG. 6generates a story embedding and relies on the user embedding being inthe joint space, thereby directly comparable to the story embedding.network

The term “negative” in FIG. 8 is used as an example story that has anegative interaction, e.g., the user was presented with the story butdid not interact (e.g., click, read) with the story, as opposed to a“positive” story in which the user positively interacted with the databy reading to completion, viewing it for a long duration of time,bookmarking or saving it, and so on. In some example embodiments, thestory data used for training is pre-partitioned into positive andnegatives sets, and two story items (one negative for negative storyembedding network 810 and one positive for positive story embeddingnetwork 805) are used per training iteration to train the model. Duringtraining, respective embeddings (e.g., positive story embedding S_(E),user embedding U_(E), and negative story embedding N_(E)) are input intothe training layers 815 for application of the training Siamese distancebased objective function (via gradient descent) as discussed above. Insome example embodiments, the training operations for architecture 800are configured as follows:

-   ::::Repeat n Times for All Training Data:::

1. Sample a user (e.g., E_(E))

2. Sample two items from the items that user has interacted with (e.g.,select a positively interacted with story and a negatively interactedstory).

3. Input user and item data into model

4. Compute distances between item embeddings and the user embedding (seedistance function in objective function above).

5. Weight these distances by the difference in the multiplier scores(see multiplication operations in objective function and in FIG. 8 )

6. (a) Take the difference between these weighted distance (seesubtraction operation in objective function and in FIG. 8 ), also (b):Add a sigmoid to represent class probabilities and to stabilize thenumerical properties, also (c) Add a logarithm to transform tolog—likelihood to further stabilize the numerical properties

7. Use the result as an error score, compute gradients, and update basedon a stochastic gradient descent scheme

8. Repeat for further data items (e.g., n times) until model is refinedor training data is exhausted.

After training, the user embedding network 705 is trained for the sharedor joint embedding space and can generate new user embeddings as newinteraction data is created. Further, after training, to create newstory embeddings, the simplified item embedding of network 600 can beimplemented to generate new content embeddings (e.g., the positive storyembedding network 805 and negative story embedding network 810, andtraining layers 815 are not used after the training procedure iscomplete and the model is created).

FIG. 9 shows example internal functional engines of a joint embeddingsystem 210, according to some example embodiments. In the exampleillustrated, the joint embedding system 21.0 comprises an interfaceengine 905, a user embedding engine 910, an item embeddings engine 915,a training engine 920, a nearest neighbor engine 925, and a networkengine 930. The interface engine 905 manages receiving interactions froma user. The user embedding engine 910 manages generating a userembedding using user embedding network 700. The item embedding engine915 manages generating item embeddings using an item embedding network600. The training engine 920 handles training the model in the jointembedding space using the training architecture 800 in FIG. 8 . Thenearest neighbor engine 925 manages finding which item embeddingnetworks are nearest neighbors to a given user's user embedding (e.g.,via Euclidean distance, inner product distance in shared embeddingspace, k nearest neighbor neural network, or other distance mechanisms).The network engine 930 manages generating a request for content ortransmitting a response to a client device. In some example embodiments,one or more engines of the joint embedding system 150 are hosted or runon the server side. For example, in some example embodiments, thetraining engine 920, item embedding engine 915, and nearest neighborengine 925 are managed by the server-side joint embedding system 150 andthe user embedding engine 910 manages the user data locally on theclient device 102. In those embodiments, the client-side joint embeddingsystem 210 transmits a request for content to the server side jointembeddings system 150, where the request includes the user embedding,which is anonymous as discussed above.

FIG. 10 shows a flow diagram for a method 1000 for recommending contentusing a joint embedding, according to some example embodiments. Atoperation 1005, the client-side system 210 stores the story embeddingsgenerated by the server-side system 150 (e.g., by item embedding 915 astrained by training engine 920 on the server side). At operation 1010,the user embedding engine 910 generates a user embedding and stores thehidden state data of the user interaction history on the client device.

At operation 1015, the user embedding engine 910 updates the userembedding. For example, the interface engine 905 receives new userinteractions with content on the client device, and user embeddingengine 910 updates the hidden state and then generates a new updateduser embedding.

At operation 1020, the nearest neighbor engine 925 determines neareststory embeddings that are nearest to the new updated user embedding. Forexample, the nearest neighbor engine 925 computes the inner productbetween the updated user embedding and the multiple available storyembeddings to determine a set of nearest story embeddings (e.g., topthree nearest story embeddings, etc.).

At operation 1025, the nearest embeddings are ranked in order ofnearness to the updated user embedding. In some example embodiments,operation 1025 is omitted where the nearest story embeddings areautomatically ranked in the nearest neighbor operation (e.g., operation1020).

At operation 1030, the interface engine 905 displays the nearest rankedstories to the user as suggestions or potential selections for the userto browse and interact.

FIG. 11 shows an example network interaction diagram 1100 for anonymouscontent updates, according to some example embodiments. With referenceto the server-side middle lane and far right late (a database lane), atoperation 1105, the server-side joint embedding system 150 generatesstory embeddings, and at operation 1110, the database server 118 storesthe embeddings in database 120.

Concurrently, with reference to the left client-side lane, at operation1115, the system 210 generates a user embedding. At operation 1120, auser of the client device interacts with new content. At operation 1125,the system 210 updates the user embedding per the new interactions. Atoperation 1130, the system 210 requests new content from the server side(e.g., from server-side joint embedding system 150).

At operation 1135, the server-side joint embedding system 150 parses therequest to request the nearest neighbors (e.g., nearest story neighborsto the user embedding). At operation 1140, the database server 118 (orserver-side joint embedding system 150, according to some exampleembodiments) sends the nearest neighbor story embeddings to the system210. At operation 1145, the system 210 displays the content, which canoptionally be ranked, to the user for selection and interaction.

FIGS. 12A-12B show example user interfaces for a joint embedding system,according to some example embodiments. In FIG. 12A, the user 1200operates a client device 102 executing the application 104, which isdisplaying stories 1215 (e.g., articles, thumbnails linked to articlesor multi-page documents) and user posts 1220. Assuming the user selectscontent item 1225, then, with reference to FIG. 1213 the content item1225 is displayed in the application 104 as shown in FIG. 12B. Assumingthe user 1200 does not like the content, the user 1200 swipes down (seedownward gesture 1240). The downward gesture 1240, the duration ofviewing time and other data can be used to update the user embedding asdiscussed above. In contrast, with reference to FIG. 12C, assume theuser selected the second content item 1230 and thoroughly interacts withit (e.g., by swiping up to watch complete video as indicated by upwardgesture 1245); the positive interactions can likewise be used to updatethe user embedding and re-rank or request new content that is nearest tothe latest most current user embedding.

With reference to FIG. 12D, in response to the updated user embedding,the application 104 (e.g., the system 210 operating within application104) finds a new content item 1280 (e.g., new nearest neighbor contentitem) and ranks it first in the stories 1215. The new content item 1280can be a result of re-ranking the items already stored locally on theclient device 102 (e.g., embedding's of the stories and thecorresponding story content stored locally), or can be new contentreceived by from the server in an anonymous content request using theuser embedding, as discussed above.

FIG. 13 is a block diagram illustrating an example software architecture1306, which may be used in conjunction with various hardwarearchitectures herein described. FIG. 13 is a non-limiting example of asoftware architecture, and it will be appreciated that many otherarchitectures may be implemented to facilitate the functionalitydescribed herein. The software architecture 1306 may execute on hardwaresuch as a machine 1400 of FIG. 14 that includes, among other things,processors, memory, and I/O components. A representative hardware layer1352 is illustrated and can represent, for example, the machine 1400 ofFIG. 14 . The representative hardware layer 1352 includes a processingunit 1354 having associated executable instructions 1304. The executableinstructions 1304 represent the executable instructions of the softwarearchitecture 1306, including implementation of the methods, components,and so forth described herein. The hardware layer 1352 also includes amemory/storage 1356, which also has the executable instructions 1304.The hardware layer 1352 may also comprise other hardware 1358.

In the example architecture of FIG. 13 , the software architecture 1306may be conceptualized as a stack of layers where each layer providesparticular functionality. For example, the software architecture 1306may include layers such as an operating system 1302, libraries 1320,frameworks/middleware 1318, applications 1516, and a presentation layer1313. Operationally, the applications 1516 and/or other componentswithin the layers may invoke API calls 1308 through the software stackand receive a response in the form of messages 1312. The layersillustrated are representative in nature and not all softwarearchitectures have all layers. For example, some mobile orspecial-purpose operating systems may not provide aframeworks/middleware 1318, while others may provide such a layer. Othersoftware architectures may include additional or different layers.

The operating system 1302 may manage hardware resources and providecommon services. The operating system 1302 may include, for example, akernel 1322, services 1324, and drivers 1326. The kernel 1322 may act asan abstraction layer between the hardware and the other software layers.For example, the kernel 1322 may be responsible for memory management,processor management (e.g., scheduling), component management,networking, security settings, and so on. The services 1324 may provideother common services for the other software layers. The drivers 1326are responsible for controlling or interfacing with the underlyinghardware. For instance, the drivers 1326 include display drivers, cameradrivers, Bluetooth® drivers, flash memory drivers, serial communicationdrivers (e.g., Universal Serial Bus (USB) drivers), Wi-Fi® drivers,audio drivers, power management drivers, and so forth depending on thehardware configuration.

The libraries 1320 provide a common infrastructure that is used by theapplications 1516 and/or other components and/or layers. The libraries1320 provide functionality that allows other software components toperform tasks in an easier fashion than by interfacing directly with theunderlying operating system 1302 functionality (e.g., kernel 1322,services 1324, and/or drivers 1326). The libraries 1320 may includesystem libraries 1344 (e.g., C standard library) that may providefunctions such as memory allocation functions, string manipulationfunctions, mathematical functions, and the like. In addition, thelibraries 1320 may include API libraries 1346 such as media libraries(e.g., libraries to support presentation and manipulation of variousmedia formats such as MPEG4, H.264, MP3, AAC, AMR, JPG, or PNG),graphics libraries (e.g., an OpenGL framework that may be used to render2D and 3D graphic content on a display), database libraries (e.g.,SQLite that may provide various relational database functions), weblibraries (e.g., WebKit that may provide web browsing functionality),and the like. The libraries 1320 may also include a wide variety ofother libraries 1348 to provide many other APIs to the applications 1516and other software components/modules.

The frameworks/middleware 1318 provide a higher-level commoninfrastructure that may be used by the applications 1516 and/or othersoftware components/modules. For example, the frameworks/middleware 1318may provide various graphic user interface (GUI) functions, high-levelresource management, high-level location services, and so forth. Theframeworks/middleware 1318 may provide a broad spectrum of other APIsthat may be utilized by the applications 1316 and/or other softwarecomponents/modules, some of which may be specific to a particularoperating system 1302 or platform.

The applications 1316 include built-in applications 1338 and/orthird-party applications 1340. Examples of representative built-inapplications 1338 may include, but are not limited to, a contactsapplication, a browser application, a book reader application, alocation application, a media application, a messaging application,and/or a game application. The third-party applications 1340 may includean application developed using the ANDROID™ or IOS™ software developmentkit (SDK) by an entity other than the vendor of the particular platform,and may be mobile software running on a mobile operating system such asIOS™, ANDROID™, WINDOWS® Phone, or other mobile operating systems. Thethird-party applications 1340 may invoke the API calls 1308 provided bythe mobile operating system (such as the operating system 1302) tofacilitate functionality described herein.

The applications 1316 may use built-in operating system functions (e.g.,kernel 1322, services 1324, and/or drivers 1326), libraries 1320, andframeworks/middleware 1318 to create user interfaces to interact withusers of the system. Alternatively, or additionally, in some systems,interactions with a user may occur through a presentation layer, such asthe presentation layer 1313. In these systems, the application/component“logic” can be separated from the aspects of the application/componentthat interact with a user.

FIG. 14 is a block diagram illustrating components of a machine 1400,according to some example embodiments, able to read instructions from amachine-readable medium (e.g., a machine-readable storage medium) andperform any one or more of the methodologies discussed herein.Specifically, FIG. 14 shows a diagrammatic representation of the machine1400 in the example form of a computer system, within which instructions1416 (e.g., software, a program, an application, an applet, an app, orother executable code) for causing the machine 1400 to perform any oneor more of the methodologies discussed herein may be executed. As such,the instructions 1414 may be used to implement modules or componentsdescribed herein. The instructions 1416 transform the general,non-programmed machine 1400 into a particular machine 1400 programmed tocarry out the described and illustrated functions in the mannerdescribed. In alternative embodiments, the machine 1400 operates as astandalone device or may be coupled (e.g., networked) to other machines.In a networked deployment, the machine 1400 may operate in the capacityof a server machine or a client machine in a server-client networkenvironment, or as a peer machine in a peer-to-peer (or distributed)network environment. The machine 1400 may comprise, but not be limitedto, a server computer, a client computer, a personal computer (PC), atablet computer, a laptop computer, a netbook, a set-top box (STB), apersonal digital assistant (PDA), an entertainment media system, acellular telephone, a smartphone, a mobile device, a wearable device(e.g., a smart watch), a smart home device (e.g., a smart appliance),other smart devices, a web appliance, a network router, a networkswitch, a network bridge, or any machine capable of executing theinstructions 1416, sequentially or otherwise, that specify actions to betaken by the machine 1400. Further, while only a single machine 1400 isillustrated, the term “machine” shall also be taken to include acollection of machines that individually or jointly execute theinstructions 1416 to perform any one or more of the methodologiesdiscussed herein.

The machine 1400 may include processors 1410, memory/storage 1430, andI/O components 1450, which may be configured to communicate with eachother such as via a bus 1402. The memory/storage 1430 may include a mainmemory 1432, static memory 1434, and a storage unit 1436, bothaccessible to the processors 1410 such as via the bus 1402. The storageunit 1436 and memory 1432 store the instructions 1416 embodying any oneor more of the methodologies or functions described herein. Theinstructions 1416 may also reside, completely or partially, within thememory 1432, within the storage unit 1436 (e.g., on machinereadable-medium 1438), within at least one of the processors 1410 (e.g.,within the processor cache memory accessible to processors 1412 or1415), or any suitable combination thereof, during execution thereof bythe machine 1400. Accordingly, the memory 1432, the storage unit 1436,and the memory of the processors 1410 are examples of machine-readablemedia.

The I/O components 1450 may include a wide variety of components toreceive input, provide output, produce output, transmit information,exchange information, capture measurements, and so on. The specific I/Ocomponents 1450 that are included in a particular machine 1400 willdepend on the type of machine. For example, portable machines such asmobile phones will likely include a touch input device or other suchinput mechanisms, while a headless server machine will likely notinclude such a touch input device. It will be appreciated that the I/Ocomponents 1450 may include many other components that are not shown inFIG. 14 . The I/O components 1450 are grouped according to functionalitymerely for simplifying the following discussion and the grouping is inno way limiting. In various example embodiments, the I/O components 1450may include output components 1452 and input components 1454. The outputcomponents 1452 may include visual components (e.g., a display such as aplasma display panel (PDP), a light-emitting diode (LED) display, aliquid-crystal display (LCD), a projector, or a cathode ray tube (CRT)),acoustic components (e.g., speakers), haptic components (e.g., avibratory motor, resistance mechanisms), other signal generators, and soforth. The input components 1454 may include alphanumeric inputcomponents (e.g., a keyboard, a touch screen configured to receivealphanumeric input, a photo-optical keyboard, or other alphanumericinput components), point-based input components (e.g., a mouse, atouchpad, a trackball, a joystick, a motion sensor, or other pointinginstruments), tactile input components (e.g., a physical button, a touchscreen that provides location and/or force of touches or touch gestures,or other tactile input components), audio input components (e.g., amicrophone), and the like.

In further example embodiments, the I/O components 1450 may includebiometric components 1456, motion components 1458, environmentcomponents 1460, or position components 1462 among a wide array of othercomponents. For example, the biometric components 1456 may includecomponents to detect expressions (e.g., hand expressions, facialexpressions, vocal expressions, body gestures, or eye tracking), measurebiosignals (e.g., blood pressure, heart rate, body temperature,perspiration, or brain waves), identify a person (e.g., voiceidentification, retinal identification, facial identification,fingerprint identification, or electroencephalogram-basedidentification), and the like. The motion components 1458 may includeacceleration sensor components (e.g., accelerometer), gravitation sensorcomponents, rotation sensor components (e.g., gyroscope), and so forth.The environment components 1460 may include, for example, illuminationsensor components (e.g., photometer), temperature sensor components(e.g., one or more thermometers that detect ambient temperature),humidity sensor components, pressure sensor components (e.g.,barometer), acoustic sensor components (e.g., one or more microphonesthat detect background noise), proximity sensor components (e.g.,infrared sensors that detect nearby objects), gas sensors (e.g., gassensors to detect concentrations of hazardous gases for safety or tomeasure pollutants in the atmosphere), or other components that mayprovide indications, measurements, or signals corresponding to asurrounding physical environment. The position components 1462 mayinclude location sensor components (e.g., a GPS receiver component),altitude sensor components (e.g., altimeters or barometers that detectair pressure from which altitude may be derived), orientation sensorcomponents (e.g., magnetometers), and the like.

Communication may be implemented using a wide variety of technologies.The I/O components 1450 may include communication components 1464operable to couple the machine 1400 to a network 1480 or devices 1470via a coupling 1482 and a coupling 1472, respectively. For example, thecommunication components 1464 may include a network interface componentor other suitable device to interface with the network 1480. In furtherexamples, the communication components 1464 may include wiredcommunication components, wireless communication components, cellularcommunication components, near field communication (NFC) components,Bluetooth® components (e.g., Bluetooth® Low Energy), Wi-Fi® components,and other communication components to provide communication via othermodalities. The devices 1470 may be another machine or any of a widevariety of peripheral devices (e.g., a peripheral device coupled via aUSB).

Moreover, the communication components 1464 may detect identifiers orinclude components operable to detect identifiers. For example, thecommunication components 1464 may include radio frequency identification(RFID) tag reader components, NFC smart tag detection components,optical reader components (e.g., an optical sensor to detectone-dimensional barcodes such as Universal Product Code (UPC) barcode,multi-dimensional barcodes such as Quick Response (QR) code, Aztec code,Data Matrix, Dataglyph, MaxiCode, PDF418, Ultra Code, UCC RSS-2Dbarcode, and other optical codes), or acoustic detection components(e.g., microphones to identify tagged audio signals). In addition, avariety of information may be derived via the communication components1464, such as location via Internet Protocol (IP) geolocation, locationvia Wi-Fi® signal triangulation, location via detecting an NFC beaconsignal that may indicate a particular location, and so forth.

“CARRIER SIGNAL” in this context refers to any intangible medium that iscapable of storing, encoding, or carrying instructions 1416 forexecution by the machine 1400, and includes digital or analogcommunications signals or other intangible media to facilitatecommunication of such instructions 1416. Instructions 1416 may betransmitted or received over the network 1480 using a transmissionmedium via a network interface device and using any one of a number ofwell-known transfer protocols.

“CLIENT DEVICE” in this context refers to any machine 1400 thatinterfaces to a network 1480 to obtain resources from one or more serversystems or other client devices 102. A client device 102 may be, but isnot limited to, a mobile phone, desktop computer, laptop, PDA,smartphone, tablet, ultrabook, netbook, multi-processor system,microprocessor-based or programmable consumer electronics system, gameconsole, set-top box, or any other communication device that a user mayuse to access a network 1480.

“COMMUNICATIONS NETWORK” in this context refers to one or more portionsof a network 1480 that may be an ad hoc network, an intranet, anextranet, a virtual private network (VPN), a local area network (LAN), awireless LAN (WLAN), a wide area network (WAN), a wireless WAN (WWAN), ametropolitan area network (MAN), the Internet, a portion of theInternet, a portion of the Public Switched Telephone Network (PSTN), aplain old telephone service (POTS) network, a cellular telephonenetwork, a wireless network, a Wi-Fi® network, another type of network,or a combination of two or more such networks. For example, a network ora portion of a network 1480 may include a wireless or cellular networkand the coupling 1482 may be a Code Division Multiple Access (CDMA)connection, a Global System for Mobile communications (GSM) connection,or another type of cellular or wireless coupling. In this example, thecoupling may implement any of a variety of types of data transfertechnology, such as Single Carrier Radio Transmission Technology(1xRTT), Evolution-Data Optimized (EVDO) technology, General PacketRadio Service (GPRS) technology, Enhanced Data rates for GSM Evolution(EDGE) technology, third Generation Partnership Project (3GPP) including3G, fourth generation wireless (4G) networks, Universal MobileTelecommunications System (UMTS), High-Speed Packet Access (HSPA),Worldwide Interoperability for Microwave Access (WiMAX), Long-TermEvolution (LTE) standard, others defined by various standard-settingorganizations, other long-range protocols, or other data transfertechnology.

“EPHEMERAL MESSAGE” in this context refers to a message 400 that isaccessible for a time-limited duration. An ephemeral message 502 may bea text, an image, a video, and the like. The access time for theephemeral message 502 may be set by the message sender. Alternatively,the access time may be a default setting, or a setting specified by therecipient. Regardless of the setting technique, the message 400 istransitory.

“MACHINE-READABLE MEDIUM” in this context refers to a component, adevice, or other tangible media able to store instructions 1416 and datatemporarily or permanently and may include, but is not limited to,random-access memory (RAM), read-only memory (ROM), buffer memory, flashmemory, optical media, magnetic media, cache memory, other types ofstorage (e.g., erasable programmable read-only memory (EPROM)), and/orany suitable combination thereof. The term “machine-readable medium”should be taken to include a single medium or multiple media (e.g., acentralized or distributed database, or associated caches and servers)able to store instructions 1416. The term “machine-readable medium”shall also be taken to include any medium, or combination of multiplemedia, that is capable of storing instructions 1416 (e.g., code) forexecution by a machine 1400, such that the instructions 1416, whenexecuted by one or more processors 1410 of the machine 1400, cause themachine 1400 to perform any one or more of the methodologies describedherein. Accordingly, a “machine-readable medium” refers to a singlestorage apparatus or device, as well as “cloud-based” storage systems orstorage networks that include multiple storage apparatus or devices. Theterm “machine-readable medium” excludes signals per se.

“COMPONENT” in this context refers to a device, a physical entity, orlogic having boundaries defined by function or subroutine calls, branchpoints, APIs, or other technologies that provide for the partitioning ormodularization of particular processing or control functions. Componentsmay be combined via their interfaces with other components to carry outa machine process. A component may be a packaged functional hardwareunit designed for use with other components and a part of a program thatusually performs a particular function of related functions. Componentsmay constitute either software components (e.g., code embodied on amachine-readable medium) or hardware components.

A “hardware component” is a tangible unit capable of performing certainoperations and may be configured or arranged in a certain physicalmanner. In various example embodiments, one or more computer systems(e.g., a standalone computer system, a client computer system, or aserver computer system) or one or more hardware components of a computersystem (e.g., a processor 1412 or a group of processors 1410) may beconfigured by software (e.g., an application or application portion) asa hardware component that operates to perform certain operations asdescribed herein. A hardware component may also be implementedmechanically, electronically, or any suitable combination thereof. Forexample, a hardware component may include dedicated circuitry or logicthat is permanently configured to perform certain operations. A hardwarecomponent may be a special-purpose processor, such as afield-programmable gate array (FPGA) or an application-specificintegrated circuit (ASIC). A hardware component may also includeprogrammable logic or circuitry that is temporarily configured bysoftware to perform certain operations. For example, a hardwarecomponent may include software executed by a general-purpose processoror other programmable processor. Once configured by such software,hardware components become specific machines (or specific components ofa machine 1400) uniquely tailored to perform the configured functionsand are no longer general-purpose processors 1410.

It will be appreciated that the decision to implement a hardwarecomponent mechanically, in dedicated and permanently configuredcircuitry, or in temporarily configured circuitry (e.g., configured bysoftware) may be driven by cost and time considerations. Accordingly,the phrase “hardware component” (or “hardware-implemented component”)should be understood to encompass a tangible entity, be that an entitythat is physically constructed, permanently configured (e.g.,hardwired), or temporarily configured (e.g., programmed) to operate in acertain manner or to perform certain operations described herein.

Considering embodiments in which hardware components are temporarilyconfigured (e.g., programmed), each of the hardware components need notbe configured or instantiated at any one instance in time. For example,where a hardware component comprises a general-purpose processor 1412configured by software to become a special-purpose processor, thegeneral-purpose processor 1412 may be configured as respectivelydifferent special-purpose processors (e.g., comprising differenthardware components) at different times. Software accordingly configuresa particular processor 1412 or processors 1410, for example, toconstitute a particular hardware component at one instance of time andto constitute a different hardware component at a different instance oftime.

Hardware components can provide information to, and receive informationfrom, other hardware components. Accordingly, the described hardwarecomponents may be regarded as being communicatively coupled. Wheremultiple hardware components exist contemporaneously, communications maybe achieved through signal transmission (e.g., over appropriate circuitsand buses) between or among two or more of the hardware components. Inembodiments in which multiple hardware components are configured orinstantiated at different times, communications between or among suchhardware components may be achieved, for example, through the storageand retrieval of information in memory structures to which the multiplehardware components have access. For example, one hardware component mayperform an operation and store the output of that operation in a memorydevice to which it is communicatively coupled. A further hardwarecomponent may then, at a later time, access the memory device toretrieve and process the stored output. Hardware components may alsoinitiate communications with input or output devices, and can operate ona resource (e.g., a collection of information).

The various operations of example methods described herein may beperformed, at least partially, by one or more processors 1410 that aretemporarily configured (e.g., by software) or permanently configured toperform the relevant operations. Whether temporarily or permanentlyconfigured, such processors 1410 may constitute processor-implementedcomponents that operate to perform one or more operations or functionsdescribed herein. As used herein, “processor-implemented component”refers to a hardware component implemented using one or more processors1410. Similarly, the methods described herein may be at least partiallyprocessor-implemented, with a particular processor 1412 or processors1410 being an example of hardware. For example, at least some of theoperations of a method may be performed by one or more processors 1410or processor-implemented components. Moreover, the one or moreprocessors 1410 may also operate to support performance of the relevantoperations in a “cloud computing” environment or as a “software as aservice” (SaaS). For example, at least some of the operations may beperformed by a group of computers (as examples of machines 1400including processors 1410), with these operations being accessible via anetwork 1480 (e.g., the Internet) and via one or more appropriateinterfaces (e.g., an API). The performance of certain of the operationsmay be distributed among the processors 1410, not only residing within asingle machine 1400, but deployed across a number of machines 1400. Insome example embodiments, the processors 1410 or processor-implementedcomponents may be located in a single geographic location (e.g., withina home environment, an office environment, or a server farm). In otherexample embodiments, the processors 1410 or processor-implementedcomponents may be distributed across a number of geographic locations.

“PROCESSOR” in this context refers to any circuit or virtual circuit (aphysical circuit emulated by logic executing on an actual processor1412) that manipulates data values according to control signals (e.g.,“commands,” “op codes,” “machine code,” etc.) and which producescorresponding output signals that are applied to operate a machine 1400.A processor may, for example, be a central processing unit (CPU), areduced instruction set computing (RISC) processor, a complexinstruction set computing (CISC) processor, a graphics processing unit(GPU), a digital signal processor (DSP), an ASIC, a radio-frequencyintegrated circuit (RFIC), or any combination thereof. A processor 1410may further be a multi-core processor 1410 having two or moreindependent processors (sometimes referred to as “cores”) that mayexecute instructions 1416 contemporaneously.

“TIMESTAMP” in this context refers to a sequence of characters orencoded information identifying when a certain event occurred, forexample giving date and time of day, sometimes accurate to a smallfraction of a second.

1. A method performed on a user device, the method comprising:generating, using a user embedding neural network, a user embedding withuser attribute data as a first input and user interactions as a secondinput; receiving an indication of a user interaction performed on acontent item; generating, using the user embedding neural network, anupdated user embedding based on the user interaction and the contentitem; identifying one or more content items using the updated userembedding and content embeddings, wherein the content embeddings and theupdated user embedding share a joint embedding space, and wherein thecontent embeddings are generated using a content embeddings neuralnetwork, and wherein the user embedding neural network is trainedjointly with the content embedding neural network; and storing, on theuser device, the identified one or more content items.
 2. The method ofclaim 1 wherein the user embedding neural network is a feed forward (FF)neural network.
 3. The method of claim 1 further comprising: updating,using a recurrent neural network, a user interaction representationbased on the user interaction, the content item, and a hidden userinteraction state.
 4. The method of claim 1 wherein the contentembeddings neural network comprises two or more content embedding neuralnetworks, the two or more content embedding neural networkscorresponding to two or more content types.
 5. The method of claim 1,wherein the one or more content items are identified by determining oneor more content embeddings of the content embeddings as nearestneighbors to the updated user embedding in the joint embedding space,the one or more content embeddings corresponding to the one or morecontent items, wherein the one or more content items are input to thecontent embeddings neural network with the one or more contentembeddings as output.
 6. The method of claim 5, wherein determining theone or more content embeddings as the nearest neighbors comprisesdetermining one or more distances from the updated user embedding to theone or more content embeddings in the joint embedding space.
 7. Themethod of claim 1 wherein the one or more content items are identifiedby: transmitting, to a network platform, a request for content itemsnearest to the updated user embedding; and receiving, from the networkplatform, the one or more content items as nearest neighbors.
 8. Themethod of claim 1, further comprising: displaying, on the user device,the one or more content items.
 9. The method of claim 1, wherein thecontent item and the one or more content items comprise one or more of:an electronic document, an image, a sequence of images, a slide show, avideo, or an audio file.
 10. The method of claim 1, wherein the contentembeddings are first content embeddings, wherein the user embeddingsneural network is trained jointly with the content embedding neuralnetwork, and wherein the training is based on determining distancesbetween a series of user embeddings and second content embeddings, thesecond content embeddings generated as output from the content embeddingneural network with input of second content items in which a userindicated an interest.
 11. The method of claim 10 wherein the series ofuser embeddings are generated based on updating the user embedding basedon interactions of the user with the second content items.
 12. Themethod of claim 10 wherein the user is determined to have indicated theinterest in the second content items based on the user performing, witheach content item of the second content items, one or more of: readingthe each content item to completion, viewing the each content item for aduration of time above a threshold duration, bookmarking the eachcontent item, or saving the each content item.
 13. The method of claim12 wherein the training is further based on determining second distancesbetween the series of user embeddings and third content embeddings, thethird content embeddings generated as second output from the contentembeddings neural network with a second input of third content items inwhich the user indicated a lack of interest.
 14. The method of claim 13wherein the user is determined to have indicated the lack of interest inthe third content items based on the user performing, with each contentitem of the third content items, one or more of the following group: notselecting the each content item when presented with the each contentitem, not reading the each content item, viewing the each content itemfor a duration of time below a threshold duration, and selecting aninterface item indicating that the user is not interested in the eachcontent item.
 15. A non-transitory machine-readable storage deviceembodying instructions that, when executed by one or more processors ofa user device, cause the one or more processors to perform operationscomprising: generating, using a user embedding neural network, a userembedding with user attribute data as a first input and userinteractions as a second input; receiving an indication of a userinteraction performed on a content item; generating, using the userembedding neural network, an updated user embedding based on the userinteraction and the content item; identifying one or more content itemsusing the updated user embedding and content embeddings, wherein thecontent embeddings and the updated user embedding share a jointembedding space, and wherein the content embeddings are generated usinga content embeddings neural network, and wherein the user embeddingneural network is trained jointly with the content embedding neuralnetwork; and storing, on the user device, the identified one or morecontent items.
 16. The non-transitory machine-readable storage device ofclaim 15 wherein the user embedding neural network is a feed forward(FF) neural network.
 17. A user device comprising: one or moreprocessors; and a memory storing instructions that, when executed by theone or more processors, cause the one or more processors to performoperations comprising: generating, using a user embedding neuralnetwork, a user embedding with user attribute data as a first input anduser interactions as a second input; receiving an indication of a userinteraction performed on a content item; generating, using the userembedding neural network, an updated user embedding based on the userinteraction and the content item; identifying one or more content itemsusing the updated user embedding and content embeddings, wherein thecontent embeddings and the updated user embedding share a jointembedding space, and wherein the content embeddings are generated usinga content embeddings neural network, and wherein the user embeddingneural network is trained jointly with the content embedding neuralnetwork; and storing, on the user device, the identified one or morecontent items.
 18. The user device of claim 17 wherein the userembedding neural network is a feed forward (FF) neural network.
 19. Theuser device of claim 17 wherein the operations further comprise:updating, using a recurrent neural network, the user interactionrepresentation based on the user interaction, the content item, and ahidden user interaction state.
 20. The user device of claim 17 whereinthe content embeddings neural network comprises two or more contentembedding neural networks, the two or more content embedding neuralnetworks corresponding to two or more content types.